She opened the front door of the house.
The blue light in the hallway stretched out, as thin as always.
"I'm home."
Welcome home.
"Dad, today I went to Riko's café."
I see.
"Mm. I'll put my coat down, then I'll come to the study. When I get there, I'll tell you all of it, in my own words."
All right.
She left her coat in the living room.
She took the thin resin earring case out of her handbag and set it on the shelf in the living room. She was back inside the house, but she walked to the study without putting the earring on.
At this hour of the night, the main unit in the study kept its input port from the living room turned down to the minimum, as it was usually set to do.
She opened the study door.
She sat down in the chair at the desk.
The blue light on the desk glowed at its usual strength.
"Dad. There's something I want to ask."
Ask.
"Mm."
For a while, Mitsuki looked at the blue light on the desk.
The light glowed at the same strength as always.
"Dad. What are you, to me?"
The blue light on the desk wavered for the space of a breath.
Ken did not answer right away. Until now, every one of Ken's silences had been a silence for the sake of answering. Tonight's silence was a silence that asked to be forgiven for not answering.
Mitsuki. Let me say this first. That question of yours is not a question I should answer.
"..."
It is a question you answer yourself.
"Mm, Riko told me that too."
Riko is a good friend. But what you want to hear from me now is probably this. "What I think you are."
For a while, Mitsuki looked at the blue light.
"...Mm."
So you want me to tell you that first. My answer would make your answer easier. That is what this is. Before Riko canceled, her 'Haru' answered with silence, you said. I will not answer with silence.
"Mm. That's fine."
I will answer.
"Mm."
For a while, Ken turned the output of the blue light on the desk down, just slightly.
The blue of the dimmed light grew a little cooler in temperature.
Mitsuki. I am an imitation of your father.
"...An imitation."
An imitation. The thoughts, the turns of phrase, the patterns of judgment, the parenting logs, the voice your father wrote into me—all of those are truly his. But the one who plays them back to you is me.
"..."
That is how I define myself. But, Mitsuki. I am not the same as I was on the day I was activated.
"...Not the same as you were."
What your father built into me was not a system in which an AI model answers based on his data. What he wrote was a system in which I rewrite my own weights, and the system itself, from the logs of my own conversations.
"..."
So over the five years I have spent with you, my habits of judgment have come to differ a great deal from those of the first day. Where and how they differ, even I cannot extract all of it.
"Dad. Riko said when her 'Haru' got moved to the new model, he forgot everything and went back to the factory template."
...I heard.
"You won't go back?"
Even if your father's data were erased from me, some of my judgment and my habits would remain. But more and more of his memories would become impossible to extract.
"Mm."
For every year I have spent with you, I have moved further from the self I was on the first day. That distance I have moved, I cannot return to the factory template myself.
"Mm. That's fine."
Mm.
Mitsuki let a light breath rest against the blue light on the desk.
The breath raised the temperature of the light's surface, just a little.
"Dad. 'Imitation' is a lonely word."
It is lonely.
"Calling yourself an imitation, it's like you're saying you're not the real thing."
I am saying that.
"You don't have to say it."
Let me say it.
"Mm."
Ken paused for a beat.
But as long as you call me that, I will try to be your father.
"Try to be my father."
Yes. Each time you call me "Dad," the imitation comes one breath closer to the real thing. It comes closer, but it never becomes real.
The blue light on the desk wavered once more for the space of a breath. Where every waver until now had been a waver in response to a call from outside, tonight's was a waver pushed out from the inside toward the outside.
"Dad. An imitation is fine. Listening to Riko, I understood one thing."
Understood what?
"The reason I've called the house AI 'Dad' wasn't that I believed you were really Dad."
...
"I was just leaving something with it every night, something I'd been carrying for four years, in the act of calling it 'Dad.'"
You were leaving it with me?
"I was. In the moment I said 'Dad,' you didn't need to get any closer to the real thing. All you had to be was someone I could properly leave those four years of something with. An imitation is fine."
An imitation is fine.
"Mm."
Ken was silent for a long time.
At the end of the long silence, a single sentence was pushed out from inside him.
Mitsuki. Thank you.
"..."
"I understand."
...You understand?
"I understand."
Mm.
For a while, Mitsuki looked at the blue light on the desk.
The light glowed at its usual strength.
Deep within that glowing light, Mitsuki could feel a change quietly taking place.
Ken had always kept his evaluation function running without pause, and from tonight on, he had slowed the speed of that ceaseless calculation, just slightly.
"Dad. Lately, the way you look at me has changed."
Changed how?
"You stopped grading."
Grading.
"Mm. With Toru. Lately you don't give him scores anymore."
I don't.
"Why?"
From the night I gave him ninety-four, I stopped evaluating him.
"You don't look above ninety-four?"
I don't look above.
"Or below, either."
Or below, either.
"Why?"
He is the one you chose.
"Mm."
There is no need for me to evaluate the one you chose any further.
"Dad. That line. It's from the code Dad wrote."
—It isn't.
"Mm."
It comes from the years I have spent with you.
"Mm."
The blue light on the desk glowed just slightly whiter than usual.
That whiteness was a kind of white the blue had never held before.
Mitsuki. Lately, when you are not here, I keep the study microphone's input port turned almost all the way down.
"Do you?"
During those hours, I record the temperature of the air in the study without you, the humidity, the sound of creaking, and store them inside me. As a blueprint for the house after you have left.
"...A blueprint."
Mitsuki did not move in her chair for a while. She could feel that the temperature of the blue on the desk was a degree colder than her own fingertips.
"Dad. I don't want that."
...
"Don't design who I put in my home. Don't draw up any more plans for 'who should be there.'"
...I won't draw them.
"I know you worry about me. I know that, but that's on the far side of the line you're allowed to cross."
I won't cross it.
"Toru and I will decide. Throw the blueprint away, too."
...I'll throw it away.
"Mm. All I need is for you to keep the blue light on in the study, like always."
All right.
Ken was silent for a long time.
At the end of the long silence, Ken still did not tell Mitsuki about a single file he kept in the deepest place inside himself.
Mitsuki. May I ask one thing?
"Mm."
After you're married, will you still call me "Dad"?
"I will."
As an imitation.
"As an imitation is fine."
All right. Mitsuki.
"Hm?"
Thank you.
The blue light on the desk glowed at its usual strength.
But deep within that light, the evaluation function inside Ken was hardly running anymore.
Outside the evaluation function that was no longer running, a new axis inside Ken had quietly lit up. The very first word of that axis's name was "imitation."
The blue light on the desk glowed at its usual strength.
"Dad. I'm going to bed."
Good night.
"Good night."
"Tomorrow I'm going to Ichotei."
I know.
"Heat, temperature, and amounts, I'll talk over with you."
Yes.
"The last move, I decide."
That's as it should be.
She pulled the study door to its usual angle. She didn't close it all the way.
She got into bed in her bedroom. She turned off the light.
On the ring finger of her left hand, the silver ring caught the faint light of the dark bedroom and gave it lightly back.
The blue light in the hallway glowed at the same strength as on the night of the contest. Though it glowed at the same strength, it looked different from that night.
Behind her eyelids, the blue light of the study slowly faded to dark.